Researchers discover genes resistant to soybean pathogen

Purdue University researchers have identified two genes within the soybean genome that are highly resistant to a soilborne pathogen that causes Phytophthora root and stem rot, a disease that costs U.S. soybean growers more than $250 million annually in lost yield.

The discovery, made by a team of scientists led by Jianxin Ma and Teresa Hughes, could lead to the development of soybean cultivars better able to withstand the pathogen Phytophthora sojae. The Purdue research was published online by Theoretical and Applied Genetics and is to appear in the journal's November print edition.

Naturally occurring Phytophthora sojae resistance exists in soybean germplasm. Most previous resistant genes, however, have lost their ability to fight off the pathogen, which has developed immunity to them. Together, the two newly identified genes appear stronger than most earlier genes and could remain viable for many more years, said Ma, a soybean geneticist in Purdue's Department of Agronomy.

"These two genes demonstrate resistance to all the predominant isolates of this pathogen found in Indiana and many other isolates that are virulent to previously identified resistance genes," he said. "If these two genes are effectively used in Indiana and other Midwest soybean crops, an annual net increase in soybean production would be anticipated."

Phytophthora sojae has been a problem for Indiana soybean farmers since it was first found in the state in 1948. The pathogen thrives in wet, cool conditions and produces spores that move in water and onto soybean roots. Diseased roots form lesions that can move up the stem and kill the entire soybean plant. The pathogen also produces spores that can remain dormant in soil through the winter and become active when warm weather returns.

Even in normal crop years Phytophthora sojae is responsible for 8-15 percent crop loss nationwide.

Because the soybean plant's own genetic resistance to Phytophthora sojae has proven to be the best way to control the pathogen, the mapping of the soybean genome in recent years has improved the odds of finding other resistant genes. But the Purdue team made its discovery looking for a genetic answer to another soybean problem, said Hughes, a U.S. Department of Agriculture plant pathologist and adjunct professor in Purdue's Department of Botany and Plant Pathology.

"We were originally looking for possible resistance to Asian soybean rust," she said. "Our experimental locations had high Phytophthora pressure, and we found that these genes did very well against that disease. That was our first clue that they might have good resistance to Phytophthora sojae."

During its three years of study the Purdue researchers have developed molecular "markers" - identifying tags - that can be used to expedite the transfer of the resistant genes to soybean cultivars. That process is known as marker-assisted selection.

"There are about 46,000 predicted gene models in what we call the reference soybean genome," Ma said. "These markers allow rapid pyramiding of multiple resistant genes into a single cultivar in order to boost the effectiveness of resistance."

Although Phytophthora sojae eventually could render the two resistant genes ineffective, the pathogen itself likely would become much weaker, Hughes said.

"Every time a pathogen overcomes resistance in its plant host it has to give up something itself," she said. "So if it turns out that in order for the pathogen to overcome this new resistance it ends up having a fitness penalty - for instance, it can't compete as well or it doesn't survive as long in the soil - then these genes will last longer.

"We believe these genes are durable, but we don't know enough about them yet to predict how effective they could be, and for how long."

Ma, Hughes and collaborating Purdue researchers Scott Abney, Feng Lin, Meixia Zhao, Jieqing Ping, Austin Johnson and Biao Zhang plan to continue their research. They next hope to move their work from greenhouses and into field trials. After that the resistant lines could make their way into commercial cultivars.

"This has the potential to provide a higher profit margin for soybean farmers, as well as reducing the use of harmful chemicals and promoting a cleaner environment," Ma said.

Related Stories

For 50 years, the world's soybean crop has depended on the use of cyst nematode resistant varieties of beans, but no one knew how these plants fought off the nematode pests. Now, the secrets of resistant soybean plants are ...

When soybean rust first appeared in the United States in late 2004, many producers feared devastating yield losses similar to losses experienced in other parts of the world. In response to this threat, researchers have been ...

When a pathogen attacks a plant, infection usually follows after the plant's immune system is compromised. A team of researchers at the University of California, Riverside focused on Phytophthora, the pathogen that triggered ...

Scientists have identified three neighboring genes that make soybeans resistant to the most damaging disease of soybean. The genes exist side-by-side on a stretch of chromosome, but only give resistance when that stretch ...

A scientific paper written by an international team of researchers led by scientists at the Virginia Bioinformatics Institute at Virginia Tech and published in the journal Science in 2006 has surpassed 200 citations in the ...

Researchers at Duke University have created a framework for helping bioengineers determine when to use multiple lines of cells to manufacture a product. The work could help a variety of industries that use bacteria to produce ...

A team of researchers with the University of Tübingen in Germany has found an example of a fish that is able to control light reflected from organs next to its pupils—a form of photolocation. In their paper published in ...

A pair of researchers with the University of Pennsylvania has found evidence suggesting humans may be evolving in a way that will prevent alcoholism in the future. In their paper published in the journal Nature Ecology & ...

0 comments

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.